|Publication number||US6998297 B2|
|Application number||US 10/866,448|
|Publication date||Feb 14, 2006|
|Filing date||Jun 11, 2004|
|Priority date||Nov 21, 1996|
|Also published as||US6407333, US20010039078, US20040222504|
|Publication number||10866448, 866448, US 6998297 B2, US 6998297B2, US-B2-6998297, US6998297 B2, US6998297B2|
|Inventors||Walter H. Schroen|
|Original Assignee||Texas Instruments Incorporated|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (16), Referenced by (2), Classifications (41), Legal Events (3)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This is a continuation of application Ser. No. 09/531,671 filed Mar. 20, 2000, abandoned, which is a divisional of application Ser. No. 08/963,769 filed Nov. 04, 1997, now U.S. Pat. No. 6,407,333, which claims priority of provisional application Ser. No. 60/031,464 filed Nov. 21, 1996.
This invention relates generally to the field of integrated circuit packaging, and more particularly to wafer level packaging of integrated circuits.
The processes involved in the fabrication and packaging of circuit chips are well known. Typically, an array of identical circuits is patterned onto a circular semiconductor wafer using well known microlithographic techniques. The wafer is then sawed into many rectangular pieces to separate the individual circuits from one another, so that each circuit occupies its own circuit chip.
The chips are individually mounted onto lead frames, where they are held in place by means of an epoxy. A wire bonder is then used to establish electrical connections between the die pads on the chip and the respective leads of the lead frame.
With the chip physically and electrically attached to the lead frame, the chip and lead frame are placed into a mold equipment, where plastic is transfer molded to surround the assembly. This plastic packaging serves to protect the chip exposure to light, moisture and contamination, which could damage the circuit components, as well as making the entire assembly mechanically rigid and durable. The molded plastic is then cured by means of heating in an oven for several hours.
The leads of the lead frame are then trimmed and formed into the desired shape. For example, the leads may be formed into a “gull wing” shape for surface-mounted chips. At this stage, various electrical and mechanical tests are performed to determine whether the chip will function for its intended purpose.
The circuit chip industry is very cost-competitive. It is therefore desirable to shorten, streamline or eliminate packaging steps to shorten production time and reduce production costs for the chips.
Accordingly, a need has arisen in the art for an improved integrated circuit packaging. The present invention provides a method of packaging integrated circuits at the wafer level. Additionally, the present invention provides a chip size package.
In accordance with the present invention, an integrated circuit package may include an integrated circuit chip. A lead frame may be opposite the circuit side of the integrated circuit chip. The lead frame may include at least one lead electrically coupled to the integrated circuit by a connector. The lead may be within a periphery of the integrated circuit chip. An encapsulate may cover the integrated circuit, the connector and a portion of the lead frame. A remaining portion of the lead frame may be exposed from the encapsulant.
More specifically, in accordance with one embodiment of the present invention, an integrated circuit may be packaged at the wafer level. In this embodiment, a sheet of lead frames may be opposite a plurality of integrated circuit chips. The encapsulate may cover the integrated circuits and a portion of each lead frame. Each encapsulated integrated circuit and opposing lead frame may form a discrete integrated circuit package.
Important technical advantages of the present invention include providing chip size packages for integrated circuits. In particular, a lead frame, connectors and encapsulant do not extend beyond a periphery of an opposing integrated circuit chip. Accordingly, package volume is minimized and the chip may be used in devices requiring extremely small chips.
Another technical advantage of the present invention includes providing a method of packaging integrated circuit chips at the wafer level. In particular, integrated circuit chips may be packaged concurrently while still part of a wafer. Accordingly, the packaging process may be carried out as a continuation of the wafer fabrication process. This serves to streamline and shorten the assembly and packaging process.
Other technical advantages will be readily apparent to one skilled in the art from the following figures, descriptions, and claims.
For a more complete understanding of the present invention and its advantages thereof, references now made to the following description taken in conjunction with the accompanying drawings, wherein like reference numerals represent like parts, in which:
The preferred embodiments of the present invention and its advantages are best understood by referring now in more detail to
The integrated circuits 14 may each include a plurality of bond pads 18 electrically coupled to the integrated circuit 14. As described in more detail below, the bond pads 18 provide electrical contacts through which the integrated circuit 14 may be connected to external components. In one embodiment, the bond pads 18 may be disposed along a center line 20 of the integrated circuit 14. In this embodiment, the number and configuration of the bond pads 18 may vary depending on the application. For example, the integrated circuit 14 may include one or more staggered or parallel rows of bond pads 18. It will be understood that the bond pads 18 may be disposed elsewhere on the integrated circuit 14 within the scope of the present invention.
Each integrated circuit 14 and surrounding section of the substrate 12 may define a discrete integrated circuit chip 22. The integrated circuit chips 22 may each be packaged to provide connections to external components and to provide protection from environmental factors. Typically, patterned wafers are sawed into individual integrated circuit chips for packaging. The integrated circuit chips are each separately mounted and coupled to a lead frame, and then encapsulated with that lead frame. A problem with this method is that the separate packaging of integrated circuit chips is both time consuming and costly. Additionally, it prevents packaging from being carried out as a continuation of the wafer fabrication process.
The present invention solves this problem by providing a method of packaging integrated circuit chips at the wafer level. As described in more detail below, the integrated circuit chips 22 are packaged concurrently while still part of the patterned wafer 10. Accordingly, the packaging process may be carried out as a continuation of the wafer fabrication process. This serves to streamline and shorten the packaging process. Moreover, as also described in more detail below, the method of the present invention produces a chip size package. As a result, the packaged integrated circuit chips 22 may be used in applications which require miniaturized devices consuming an area not larger than individual chips.
A sheet of lead frames 26 may be disposed opposite the surface 16 of the substrate 12. The sheet of lead frames 26 may include a plurality of individual lead frames 28 that each provide electrical connections for one of the integrated circuit chips 22.
The sheet of lead frames 26 may be a unitary sheet of material. In one embodiment, the material of the lead frames 28 may be Alloy 42 locally plated with silver. It will be understood that a variety of other materials may be used for the lead frames 28 within the scope of the present invention.
The lead frames 28 may each include a plurality of leads 30 within a periphery 32 of an opposing integrated circuit chip 22. Accordingly, the leads 30 do not overlap other integrated circuit chips 22. As described in more detail below, the leads 30 may be electrically coupled to the bonding pads 18 and extend from the encapsulant for connection to external components.
In one embodiment, the leads 30 may be in a dual level configuration. In this configuration, as shown by
The leads 30 may each have a distal end 34 for connection to an external device. In one embodiment, as shown by
As shown by
The lead frames 28 may each be mounted to an opposing integrated circuit chip 22. In one embodiment, an adhesive tape 40 may be used to mount the lead frames 28 to the opposing integrated circuit chip 22. Preferably, the adhesive tape 40 is non-conducting to prevent electrical shorting. The adhesive tape 40 may be tacky on both sides to adhere to the polymide layer 24 and to the leads 30 of the lead frame 28. The adhesive tape 40 may be attached to the lead frame 28 in a variety of ways and a variety of thicknesses. Such methods are well known and will not be further described.
Additionally, the upper set of leads 30 may be mounted to the lower set of leads 30 by the adhesive tape 40. Although the use of adhesive tape 40 has been discussed for mounting the leads 30, it will be understood that the lead frames 28 may be otherwise mounted to the opposing integrated circuit chip 22. Similarly, the upper leads may be otherwise mounted to the lower leads. For example, the leads 30 and/or lead frame 28 may be mechanically coupled by an epoxy or the like.
In one embodiment, the encapsulant 44 may be applied to only the side of the wafer 10 including the integrated circuits 14, connectors 42 and lead frames 28. The encapsulant 44 may be applied as a liquid by a syringe. In this embodiment, the liquid may be at first low viscosity and quickly solidify. It will be understood that the encapsulant 44 may be otherwise applied within the scope of the present invention. For example, the encapsulant 44 may be applied using conventional transfer molding or 3P molding technology, a mold cavity as large as the wafer 10 or the like. It will be further understood that both sides of the wafer 10 may be encapsulated within the scope of the present invention.
As shown by
The distal ends 34 may be left exposed by regulating the volume of encapsulant 44 applied to the wafer 10. For the embodiment of
As shown by
Although the present invention has been described with several embodiments, various changes and modifications may be suggested to one skilled in the art. It is intended that the present invention encompass such changes and modifications as fall within the scope of the appended claims.
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|U.S. Classification||438/123, 257/E23.124, 257/E23.039, 438/127, 438/124|
|International Classification||H01L23/495, H01L21/44, H01L23/31|
|Cooperative Classification||H01L2924/181, H01L2924/01005, H01L23/3107, H01L2924/01079, H01L2924/20752, H01L2924/01047, H01L24/45, H01L2224/45144, H01L2224/49109, H01L2224/94, H01L24/94, H01L2224/97, H01L24/97, H01L2224/73215, H01L23/4951, H01L2224/32014, H01L2224/48091, H01L23/3114, H01L2224/45015, H01L2924/20753, H01L2224/48247, H01L24/49, H01L2924/01078, H01L2924/14, H01L2924/01006, H01L2924/014, H01L24/48|
|European Classification||H01L24/49, H01L24/97, H01L24/94, H01L23/495A4, H01L23/31H, H01L23/31H1|
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